This invention concerns methods and products utilizing fiberous absorbent bodies for absorbing fluids. In particular, the invention concerns products for absorbing body fluids such as catamenial tampons, diapers, sanitary napkins and the like, and is specifically directed toward fiberous absorbent bodies which are easily handled in processes for manufacturing such products, which bodies exhibit increased absorbency as contrasted with commonly used fiberous bodies.
The vast majority of body fluid absorbent products now in use comprise, at least in their formative stages, pads of loosely associated fiberous and generally cellulosic absorbent materials such as comminuted wood pulp fluff, rayon staple, cotton, cotton linters and the like. For generations, these materials have proven to be useful and effective in dressings, diapers and sanitary protection devices in that these materials are absorbent, inexpensive and, in the case of absorbent products which must be worn by the user for a substantial period of time, these materials are flexible and hence comfortable. Unfortunately, balanced against such highly desirable properties, is the fact that pads manufactured from the loosely associated fiberous materials are relatively weak, have little tensile strength and must be handled gingerly throughout any product manufacturing process. Several attempts have been made to increase the structural integrity of these pads but in the main, such attempts have resulted in products which are either less absorbent or less flexible and hence represent only a compromise between the exigencies of manufacturing and the functional properties of the final product. For example, in U.S. Pat. No. 4,057,061 issued on Nov. 8, 1977 to Shigemitsu Ishikawa, a thin pad is described which comprises compressed cottony pulp fibers, the compression being taught to add to the structural integrity of the pad. This advantage notwithstanding, the thin pad, by virtue of the compression, is substantially less flexible and hence less comfortable than prior products. A similar approach has been taken in U.S. Pat. Nos. 3,065,751 issued to Gunner Gravdahl on Dec. 8, 1970; and 3,017,304 issued to A. A. Burgeni on Jan. 16, 1962 with similar results.
The manufacturing problems related to absorbent pads have increased to an extent with the development of a series of cellulosic materials which exhibit substantially increased absorptive properties by virtue of chemical modification. Examples of such materials are the grafted cellulose copolymers described in U.S. Pat. No. 3,889,678 issued to Pronoy Chatterjee et al. on June 17, 1975; and the crosslinked carboxyalkyl cellulosic materials described in U.S. Pat. Nos. 3,731,686 and 3,858,585 issued to Pronoy Chatterjee on May 8, 1973 and June 7, 1975, and in U.S. Pat. No. 3,589,364 issued to W. L. Dean et al. on June 1971. These materials are in the form of highly swellable, and highly fluid-retentive fibers. It is desirable to combine these fibers with the more conventional absorbent materials such as rayon, wood pulp, cotton or the like to produce an absorbent body having increased fluid retentive properties. Unfortunately, when mixing such fiberous materials it is not an easy processing task to get an even distribution and this has added to the burden of producing an absorbent body for the products of interest herein.
Accordingly, there is need for improvement in the manufacture of absorbent bodies specifically directed toward increasing the integrity of the bodies without sacrificing flexibility and, particularly when introducing chemically modified absorbent materials into the absorbent body.